#include "function.h"
Go to the source code of this file.
Macros | |
| #define | SHRINK_WRAPPING_ENABLED (flag_shrink_wrap && targetm.have_simple_return ()) |
Functions | |
| bool | requires_stack_frame_p (rtx_insn *, HARD_REG_SET, HARD_REG_SET) |
| void | try_shrink_wrapping (edge *entry_edge, rtx_insn *prologue_seq) |
| void | try_shrink_wrapping_separate (basic_block first_bb) |
| bool | use_shrink_wrapping_separate (void) |
Macro Definition Documentation
◆ SHRINK_WRAPPING_ENABLED
| #define SHRINK_WRAPPING_ENABLED (flag_shrink_wrap && targetm.have_simple_return ()) |
Function Documentation
◆ requires_stack_frame_p()
|
extern |
Shrink-wrapping related functions. Copyright (C) 1989-2025 Free Software Foundation, Inc. This file is part of GCC. GCC is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3, or (at your option) any later version. GCC is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with GCC; see the file COPYING3. If not see <http://www.gnu.org/licenses/>.
In shrink-wrap.cc.
Shrink-wrapping related optimizations. Copyright (C) 1987-2025 Free Software Foundation, Inc. This file is part of GCC. GCC is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3, or (at your option) any later version. GCC is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with GCC; see the file COPYING3. If not see <http://www.gnu.org/licenses/>.
This file handles shrink-wrapping related optimizations.
Return true if INSN requires the stack frame to be set up. PROLOGUE_USED contains the hard registers used in the function prologue. SET_UP_BY_PROLOGUE is the set of registers we expect the prologue to set up for the function.
References add_to_hard_reg_set(), CALL_P, can_throw_internal(), cfun, CLEAR_HARD_REG_SET, crtl, DF_REF_REG, df_regs_ever_live_p(), FAKE_CALL_P, FOR_EACH_INSN_DEF, FOR_EACH_INSN_USE, GET_MODE, hard_reg_set_intersect_p(), REG_P, REGNO, SIBLING_CALL_P, and TEST_HARD_REG_BIT.
Referenced by try_shrink_wrapping().
◆ try_shrink_wrapping()
Try to perform a kind of shrink-wrapping, making sure the
prologue/epilogue is emitted only around those parts of the
function that require it.
There will be exactly one prologue, and it will be executed either
zero or one time, on any path. Depending on where the prologue is
placed, some of the basic blocks can be reached via both paths with
and without a prologue. Such blocks will be duplicated here, and the
edges changed to match.
Paths that go to the exit without going through the prologue will use
a simple_return instead of the epilogue. We maximize the number of
those, making sure to only duplicate blocks that can be duplicated.
If the prologue can then still be placed in multiple locations, we
place it as early as possible.
An example, where we duplicate blocks with control flow (legend:
_B_egin, _R_eturn and _S_imple_return; edges without arrowhead should
be taken to point down or to the right, to simplify the diagram; here,
block 3 needs a prologue, the rest does not):
B B
| |
2 2
|\ |\
| 3 becomes | 3
|/ | \
4 7 4
|\ |\ |\
| 5 | 8 | 5
|/ |/ |/
6 9 6
| | |
R S R
(bb 4 is duplicated to 7, and so on; the prologue is inserted on the
edge 2->3).
Another example, where part of a loop is duplicated (again, bb 3 is
the only block that needs a prologue):
B 3<-- B ->3<--
| | | | | | |
| v | becomes | | v |
2---4--- 2---5-- 4---
| | |
R S R
(bb 4 is duplicated to 5; the prologue is inserted on the edge 5->3).
ENTRY_EDGE is the edge where the prologue will be placed, possibly
changed by this function. PROLOGUE_SEQ is the prologue we will insert.
References add_to_hard_reg_set(), any_condjump_p(), profile_count::apply_scale(), basic_block_def::aux, BB_COPY_PARTITION, BB_END, bitmap_bit_p, bitmap_copy(), bitmap_set_bit, calculate_dominance_info(), can_dup_for_shrink_wrapping(), can_get_prologue(), CDI_DOMINATORS, CDI_POST_DOMINATORS, cfun, CLEAR_HARD_REG_BIT, CLEAR_HARD_REG_SET, basic_block_def::count, create_empty_bb(), crtl, dominated_by_p(), dump_file, duplicate_block(), EDGE_COUNT, ei_next(), ei_safe_edge(), ei_start, emit_barrier_after_bb(), ENTRY_BLOCK_PTR_FOR_FN, EXIT_BLOCK_PTR_FOR_FN, FOR_BB_INSNS, FOR_EACH_BB_FN, FOR_EACH_BB_REVERSE_FN, FOR_EACH_EDGE, force_nonfallthru(), frame_pointer_needed, free_dominance_info(), gcc_assert, get_immediate_dominator(), GET_MODE, get_uncond_jump_length(), handle_simple_exit(), HARD_FRAME_POINTER_REGNUM, basic_block_def::index, INSN_UID(), INVALID_REGNUM, JUMP_P, make_single_succ_edge(), n_basic_blocks_for_fn, nearest_common_dominator(), NEXT_INSN(), NONDEBUG_INSN_P, profile_count::nonzero_p(), NOTE_KIND, NOTE_P, note_stores(), note_uses(), NULL, PATTERN(), PIC_OFFSET_TABLE_REGNUM, pic_offset_table_rtx, basic_block_def::preds, prepare_shrink_wrap(), print_rtl_single(), record_hard_reg_sets(), record_hard_reg_uses(), redirect_edge_and_branch_force(), REGNO, requires_stack_frame_p(), hard_reg_set_container::set, SHRINK_WRAPPING_ENABLED, single_succ_edge(), split_edge(), basic_block_def::succs, targetm, and profile_count::zero().
Referenced by thread_prologue_and_epilogue_insns().
◆ try_shrink_wrapping_separate()
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extern |
The main entry point to this subpass. FIRST_BB is where the prologue would be normally put.
References bitmap_and_compl(), bitmap_empty_p(), calculate_dominance_info(), CDI_DOMINATORS, CDI_POST_DOMINATORS, crtl, df_analyze(), df_live_add_problem(), df_live_set_all_dirty(), df_scan, DF_SCAN_EMPTY_ENTRY_EXIT, df_update_entry_exit_and_calls(), disqualify_problematic_components(), dump_components(), dump_file, emit_common_heads_for_components(), emit_common_tails_for_components(), EXECUTE_IF_SET_IN_BITMAP, fini_separate_shrink_wrap(), free_dominance_info(), sw::has_components, init_separate_shrink_wrap(), insert_prologue_epilogue_for_components(), place_prologue_for_one_component(), sbitmap_free(), spread_components(), SW(), targetm, and use_shrink_wrapping_separate().
Referenced by thread_prologue_and_epilogue_insns().
◆ use_shrink_wrapping_separate()
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extern |
References cfun, crtl, optimize_function_for_speed_p(), SHRINK_WRAPPING_ENABLED, and targetm.
Referenced by try_shrink_wrapping_separate().
